In many premium power applications and power distribution systems, it is desirable to monitor individual branch circuit currents that distribute power from a main line to various circuit loads in an electrical system. An operator can be informed as to which connected loads are in operation, whether connected equipment is idling or fully operating, and whether any individual circuit is approaching overload and should be remedied.
In collecting data from many scattered circuit loads, current transformers (CTs) are often mounted in the system to gather current flow information. A typical mount is within the circuit breaker panel enclosure, where multiple branches from circuit breakers in the panel can be conveniently monitored from a single location. Thus, a main power supply enters the circuit breaker panel and the power is split into multiple branches having circuit breakers protecting each branch. The CTs are mounted electrically downstream of the circuit breakers in a long circuit board placed adjacent the circuit breakers. In many industrial or data center applications, the connected loads are rarely turned off to be serviced or repaired. Consequently, the reliability of the CTs with their respective board must be very high, since the CTs are toroidal in nature and cannot be removed without disconnecting circuit wiring and interrupting critical power to loads.
In application, relatively thick wire is fed from the electrical load into the circuit breaker panel, through the appropriate CT for a particular branch, and then into the contacts for the circuit breaker. However, there are several challenges. For example:                1. The standard 42-pole panel for circuit breakers has limited space within its housing, typically resulting in the CT board with the corresponding CTs being made long and thin and thereby mechanically weak. Stability and integrity of the system is compromised by the relative weakness of the CT board.        2. High voltage terminations at the individual circuit breaker outputs are very close to exposed current sensor soldered connections and thereby risk dangerous voltages entering the low-voltage control circuit wiring and destroying aspects of the electrical circuit and/or creating a safety hazard.        3. Typical CT boards require many extra soldered connections, directly lowering reliability and performance due to lack of mechanical strength.        
Branch circuit monitors to date, such as those disclosed in U.S. Pat. Nos. 6,330,516 and 6,809,509, have been built on printed circuit boards and thereby posses the disadvantages listed above. The circuit board is thin and tends to flex as thick branch circuit wires pass through the mounted CTs and can break the soldered connections, seriously impairing the performance of the branch circuit monitor.
For example, FIGS. 1A and 1B are schematic front and end views, respectively, of a prior art arrangement. A circuit breaker panel 2 contains a circuit breaker assembly 4 having a plurality of circuit breakers 6, 8. Conductive wires 10, 12 (relatively thick wires depending on the power requirements) feed power from the circuit breakers to loads 14, 16. A circuit board 20 having CTs 22, 24 mounted thereon is used to measure current of the wires 10, 12 passing through the CTs 22, 24 between the circuit breakers and the loads. The CTs can eventually connect to an output connector 18 starting with an output wire 26 from the CT coil wire that is soldered to a pin 28 at a soldered connection 32. The CT with the pin is assembled to the circuit board 20 by generally extending the pin 28 through a hole in the circuit board and soldering the pin to the circuit board at a soldered connection 34. The soldered connection 34 is in turn connected to a circuit board line (not shown) formed on the circuit board 20 that leads to another soldered connection at the output connector 18. A ribbon cable (not shown) can connect to the output connector 18 to carry output from the individual CTs to a monitoring system.
Each CT conductive path to the output connector has therefore three soldered connections and each CT has two wires for a total of six soldered connections per CT. Generally, there are 21 CTs on a circuit board for 21 circuit breakers, resulting in at least 126 soldered connections per board. For the modem trend of a circuit breaker panel having 42 circuit breakers in line, there are 252 soldered connections for such a typical circuit board branch monitoring system.
The bending stress 30 caused by pulling the thick wires 10, 12 through the CTs is concentrated on the CTs 22, 24 and its soldered connections, such as connection 28, resulting in damage to the unit and therefore the system, more frequently than is desirable. Also, connections on the circuit board are exposed to dangerous voltages from the relatively close wires 10, 12.
Therefore, there remains a need for improvement in the method of mounting and monitoring branch distribution power in such power applications and related systems.